搜索：poj 1154 LETTERS（DFS）
【转】http://blog.csdn.net/zxy_snow/article/details/5947160
#include <stdio.h>#include <stdlib.h>#include <iostream>#include <string.h>using namespace std;int visit[30];int n,m;int step[8] = {1,0,-1,0,0,1,0,-1};int num[100][100],cou = 1,mmax = 0;;void DFS(int i, int j){for( int k=0; k<8; k+=2){int a = i+step[k];int b = j+step[k+1];if( a>=1 && a<=n && b>=1 && b<=m && !visit[num[a][b]] ){visit[num[a][b]] = 1;cou++;DFS(a,b);if( cou > mmax ) mmax = cou;cou--;visit[num[a][b]] = 0;}}}int main(void){char str[100];while( cin >> n >> m ){getchar();memset(visit,0,sizeof(visit));cou = 1; mmax = 1;for(int i=1; i<=n; i++){ gets(str);for(int k=0; k<m; k++) num[i][k+1] = str[k] -'A' + 1;}visit[num[1][1]] = 1;DFS(1,1);cout << mmax << endl;}return 0;}?